<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <div class="banner">
        <p>
            Lorem ipsum dolor sit amet, consectetur adipiscing elit. Phasellus imperdiet faucibus turpis ac accumsan.
            ornare a in lacus. </p>
        <button> Button 1</button>
        <button> Button 2</button>
    </div>
</body>

<style>
    .banner {
        --w: 700px;
        --c: (100vw - var(--w));

        color: #fff;
        background: #000e;
        padding: 10px;
        box-sizing: border-box;
        text-align: center;
        position: fixed;
        bottom: clamp(0px, var(--c)*1000, calc(100% - 10px));
        transform: translateY(clamp(0%, var(--c)*1000, 100%));
        right: clamp(0px, var(--c)*1000, 10px);
        width: clamp(300px, var(--c)*-1000, 100%);
    }

    .banner p {
        margin: 0;
        display: inline-block;
        text-align: left;
    }

    .banner button {
        border: none;
        cursor: pointer;
        background: #fff;
        color: #000;
        margin: 10px 5px 0 0;
        font-size: clamp(15px, var(--c)*1000, 20px);
        padding: 5px 20px;
    }
</style>

</html>